The present invention generally relates to the field of electronic rotational position indicator apparatus and more particularly to the field of the use of such apparatus in the electronic control of the operation of an internal combustion engine. More specifically, the present invention relates to the use of rotational position indicator apparatus in an electronic cylinder identification system which synchronizes cylinder fuel injection for an internal combustion engine.
For electronic control of the operation of an internal combustion engine, typically it is necessary to identify when the piston of a reference cylinder of a multi-cylinder engine is at a particular position in its reciprocal cycle. In fuel injection systems, typically engine fuel is injected to each cylinder at a predetermined time prior to combustion during the compression stroke of the cylinder. This predetermined time corresponds to a specific position of the cylinder piston in its reciprocal cycle, and this time also directly corresponds to a rotational position of an engine camshaft which is rotated at one half of the rotational speed of the engine crankshaft which supplies the reciprocal driving movement to the cylinder piston. In such fuel injection systems, it is necessary to identify when at least one of the engine cylinders is at a particular point in its compression cycle, then typically the fuel injection of this cylinder and the other cylinders are commenced sequentially in response to the identification of this piston position for the identified reference cylinder.
In prior fuel injection systems, complex mechanical gears have often been utilized to insure the proper synchronization of fuel injection into each of the cylinders. These mechanical systems utilize a complex series of cams that directly control the opening and closing of valves which implement fuel injection. In electronic fuel injection systems, typically electromagnetic relays are utilized to accomplish fuel injection and the control signals for these relays are derived from sensors which sense the rotational position of the engine camshaft and/or crankshaft or perform the equivalent function.
In some electronic fuel injection systems, a single cam lobe is attached to the camshaft such that it will open or close an associated switch at a predetermined rotational position of the camshaft. In this manner, a signal identifying a rotational position of the camshaft is produced and is utilized to synchronize all subsequent fuel injection since the occurrence of this camshaft pulse will directly correspond to known piston position in a reference cylinder. This type of fuel injection system has the deficiency in that it may require a full revolution of the camshaft (which corresponds to two full revolutions of the engine crankshaft) before producing a synchronizing signal to insure the proper synchronization of the fuel injection. Some systems may also substitute a cam projection and an electronic sensor for the cam lobe and switch which generates the reference pulse. The sequencing of fuel injection after the occurrence of the reference pulse is controlled, in some systems, by utilizing a single sensor cooperating with an appropriate number lobe projections on the crankshaft or by utilizing the generated spark timing pulses to provide a signal to index a sequential counter whose count is initialized (set) in accordance with the occurrence of the reference cylinder identification pulse. While many such systems are known, most of these systems suffer from the previously mentioned deficiency of potentially requiring a complete revolution of the engine camshaft before generation of the synchronization pulse. This results in requiring two engine revolutions before initiating the proper sequence of fuel injection. During the intial start-up of the engine this is certainly not desirable. Also additional circuitry may be required to generate the sequence stepping control signals once the reference cylinder has been identified, and this adds to the cost of such systems.
Some prior fuel injection systems disclosed the use of a plurality of stationary electronic sensors for operation in conjunction with a rotary projection making one complete revolution per engine cycle (thus being rotated at the camshaft rotational speed). These systems either suggest utilizing a plurality of projections having different configurations, such as an extending north magnetic pole for one projection and an extending south magnetic pole for the other projection, or they suggest utilizing a large number of camshaft sensors. In either case, while synchronization fuel injection information is obtained more rapidly than the previously discussed systems, this is accomplished by the added expense of requiring additional sensors or by requiring different camshaft projection configurations and thereby requiring sensors which can distinguish between these different projection configurations. In either event, the extra cost of these type of systems has hampered the extensive adoption of such systems.
The rapid identification of a known position for a reference cylinder is not just limited to the field of fuel injection, since some distributorless ignition systems also require the identification of a reference engine cylinder cycle position to insure the proper routing of spark ignition signals to the appropriate engine cylinders. In typical internal combustion engines which include a distributor, this spark signal routing is accomplished by the mechanical rotation of the rotor arm of the distributor. For distributorless ignition systems, reference cylinder identification circuits similar to those described above have been developed and suffer from the same above-mentioned deficiencies of generally requiring either an excessive number of stationary sensors or providing a reference signal only after an excessively large amount of engine crankshaft revolution.